digital compass modules
heiny at starband.net
Wed Jan 23 17:56:13 CET 2008
On Wednesday 23 January 2008, ground control picked up the following
transmission from luc at bos-boon.nl:
> Citeren Schmidt András <asch at freemail.hu>:
> > 1. The map of a GPS map viewer application turns when you turn
> > the machine so it is always aligned with the environment (this
> > feature is included on some GPS tools.)
> A handheld GPS use the change in position measured by GPS to
> determinate the direction of movement and is able to turn the display
> in that direction.
> In fact, when the GPS is working like it should (IE very good with
> the planned chipset) this is the best way to calculate the heading.
> Most important: it's already there in the phone.
Use case: I'm hiking in the mountains, heading 0 degrees (due north) at
5 km/h. I stop because there's something interesting off to the left,
and I want to get its exact bearing (let's assume that's something like
283 degrees). So I rotate the GPS so "up" points at the object of
Results: Handheld with internal compass (for example, many Garmin units)
can give me correct bearing to the object. Neo thinks bearing to the
object is 0 degrees, since I'm not moving and you can't compute
rotation about axis with GPS signal only.
Failure mode: Stationary GPS is more subject to false readings due to
reflection than moving GPS. Due to reflections, Neo might think I'm
moving in some random direction, and give a bogus heading that appears
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